What notes form the Gr +6 chord in C major?

The Gr +6 chord, also known as the German augmented sixth chord, is typically formed by the root, the major third, the perfect fifth, and an augmented sixth above the root. In the context of C major, the root note is C.

To build the Gr +6 chord in C major, the notes would specifically be:

1. Root: C

2. Major third: E

3. Perfect fifth: G

4. Augmented sixth: Instead of a flat sixth, which would be A♭, the German sixth uses A natural (the sixth scale degree, which is also a major sixth above the root C, making it A), creating the interval of an augmented sixth (A and C).

Thus, the notes that comprise the C Gr +6 chord are C, E, G, and A. This matches with the choice presented, making it the correct answer. The presence of the A natural alongside the C, E, and G gives the chord its characteristic sound, setting it apart from other types of chords that might include different notes.